1. Field of the Invention
The instant disclosure relates to a Single-Inductor Dual-Output power converter; in particular, to a Single-Inductor Dual-Output power converter used in the hysteresis current control mode and a control method thereof.
2. Description of Related Art
With the development of the electronics industry, the power converter has taken an important role for stabilizing the voltage of load and extending the battery life time. Moreover, because the microminiaturization of the wafer processing and the lowering of the core voltage, the voltage precision of power converter has become a strict requirement. Thus, the power converter for the hysteresis current control mode with quick transient response has become valuable. In short, the hysteresis current control mode is a switching control mode to control the inductive current to be within the predetermined upper limit threshold and the lower limit threshold. For example, when the inductive current is lower than the lower limit threshold, the power converter turns on the power switch to increase the inductive current, and when the inductive current reaches the upper limit threshold, the power converter turns off the power switch to decrease the inductive current to the lower limit threshold. Therefore, the above switching control has advantages, such as easy design, quick response needing no slope compensation, wherein its operation mode has no constant frequency.
In addition, recently, the electronic devices have become multi-functional. Thus, to effectively satisfy the power requirements of different functional elements, it has become necessary to have a power converter able to provide different voltages, wherein the single-inductor dual-output power converter is a suitable option. The single-inductor dual-output power converter can provide the boost mechanism and the buck-boost mechanism with one inductor, which saves volume, lowering the cost and increasing the converting efficiency. However, when the above inductor is used under both mechanisms, the inductive currents would be different in different loading conditions, which makes it hard to set the upper limit threshold and the lower limit threshold of the inductive current of the power switch in different loading conditions, and further makes it hard to control the turning on or off of the power switch.